Method for accurate optical treatment of an eye&#39;s fundus

ABSTRACT

A system and method is provided to accurately treat sites on an eye&#39;s retina employing computer based image generation, processing and central control means in conjunction with diode laser sources and optical fibers. The system and method accurately determine geometry of a treatment zone of a specific eye&#39;s fundus and adjust a treatment beam to irradiate the treatment zone with minimal coverage of adjacent well tissue. The treatment zone or zone is accurately determined with digital processing of angiographic data and slit lamp image data. This information is integrated with information on the treatment beam characteristics to better match treatment beam coverage with minimal overlap with healthy areas of the fundus. Additionally preferred embodiments also have the ability to automatically track eye movement and switch the beam source depending on eye movement, adjusting the beam spot area in real time.

REFERENCE TO RELATED CASE

[0001] This application is a divisional of co-pending U.S. patentapplication Ser. No. 09/569,438 filed on May 12, 2000 by Dirk Pawlowskiand Wolfgang Neuberger, inventors, entitled “SYSTEM AND METHOD FORACCURATE OPTICAL TREATMENT OF AN EYE'S FUNDUS”.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to the field of ophthalmology, inparticular to the field of optical treatment of an eye's fundus usinglasers. More specifically it deals with the application of computerbased image generation, processing and central control means toaccurately treat sites on an eye's retina, particularly its macula inconnection with diode laser sources and optical fibers.

[0004] Information Disclosure Statement

[0005] Laser methods are widely accepted in today's modem ophthalmology,as well as in pure diagnosis like laser scanning ophthalmoscopes for thetreatment of an eye. Treatment methods include laser reshaping of thecornea to correct strong myopic or presbyopic effects, laser surgery inthe eye itself and several treatments of the retina. Retina relatedmethods include coagulation laser systems and, more recently,PhotoDynamic Therapy (PDT) treatments of the retina. For examplecoagulation laser treatment can be used to re-weld the retina to the eyebackground if the retina tends to loosen from the eye background, whichcan lead to complete blindness. Another kind of therapy is to stop theso called age related macula degeneration (AMD). This disease ischaracterized by untypical blood agglomeration in the macula, the partof highest vision sensitivity of the retina. These blood agglomerationsdo still circulate, hence it is possible to make an accurate diagnosisapplying the so called fluorescence angiography. A certain fluorescingdrug is added to the patient's blood circuit and then an image of theretina is taken. The fluorescing drug allows the exact visualization ofall blood vessels on the retina and thus in particular those beingresponsible for the age related macula degeneration. This degenerationactually can not be reversed, but it can be stopped hence the completeloss of eyesight can be prevented.

[0006] A recent method is based on so called PDT means. In thistreatment, a PDT drug is introduced into the patients blood circulation.The drug is originally harmless and has usually no therapeutic effects,but it is sensitive to illumination at a certain wavelength. If light ofthis suitable wavelength is absorbed by the drug molecules, they undergoa chemical reaction to another product, which is responsible for thetherapeutic effect. In a simple case, this effect is the excitation ofthe drug molecule to an excited state where it can react with oxygen toform singlet oxygen which is highly reactive. The singlet oxygen quicklyreacts with nearby tissue to oxidize it, i.e. cause necrosis.Alternatively, the splitting of one molecule can create two radicals,which are chemically very reactive and can destroy body cells. Becausethis method is very selective, it widely prevents negative side effectsof the therapy by only illuminating the infected area. Typicalapplications apart from the therapy of the age related macula includetumor treatments, are catheter disinfection and dermatologicalapplications. Concerning the treatment of age related maculadegeneration, recently the described simple PDT method has been applied.The drug was given to the patient and after a certain time the maculawas illuminated with the beam spot of light at the critical wavelength,preferably provided by a laser or a fiber coupled diode laser. Bloodagglomeration vessels are then destroyed by the generated therapeuticsubstance and the age related macula degeneration is stopped. In U.S.Pat. No. 5,336,216 [D. A. Dewey] a method for generating a treatmentbeam spot on the retina is claimed, which in particular generates a spoton the retina which has a rectangular intensity profile, also known astop-hat profile for all sizes. This method suffers from the fact, thatthe knowledge about the treatment zone is only rudimentary. As describedin the latter the treatment can be significantly enhanced if thetreatment zone is well known.

[0007] As noted above, laser based methods of fundus treatment is widelyaccepted in today's ophthalmology and applied in different forms. Forseveral forms of the treatments focused laser beams are used, as forexample in laser abrasive cornea treatment in order to correct myopic orpresbyopic defects. Further, laser coagulation routines are performed,in order to re-weld the retina to the eye background, if it becomesunbound, which would result in complete blindness. PDT treatment is arelatively novel method to heal certain diseases of the eye. Especiallysuccessful it can be used for the correction of the so called AMD, wherecertain defects of the blood vessels in the macula can cause the maculato loose from the eye background. The photodynamic substances areintroduced to the patients blood circuit and the treatment zone isirradiated with light of a suitable wavelength in order to start alocalized treatment effect only in the region of the treatment zone.Several disadvantages are associated with the state of the art intoday's PDT methods. The most striking is the strong inaccuracy of theprocess can be attributed to the lack of means for an accuratedetermination of the treatment zone and therefore the lack of beam areagenerating devices providing the desired accuracy.

[0008] However, the state of the art illumination means are designedsuch, that it is impossible to obtain an illumination of the treatmentzone alone. The operator has to calculate from fluorescence angiographicdiagnostics how large the treatment area is, and then manually adjustthe laser beam spot size to be large enough to completely cover thetreatment area. This method is extremely inaccurate since no informationabout the specific eye is provided therein. The spot size on the retinavaries with different patient's different eyeballs, but thejustification is absolute. This problem is addressed by the presentinvention.

[0009] Since the typically used slit-lamp generated pictures are only ofmedium quality the treatment zone can be hardly noticeable therein.Hence it's size must be determined from the fluorescence angiography,but this image does not have any relation to the images generated by theslit lamp, though it is the same eyeball, for reasons of differentoptics, different viewing angles and so on. In any case, whether thetreatment is determined from the slit lamp picture or from theangiography, the error made by the calculation of the beam spot size issignificant and typically exceeds 200%.

[0010] For this reason it is obvious, that not only the treatment zoneis illuminated, but also the healthy zones in the eye. This can lead tothe destruction of important blood vessels followed by a reduction ofeyesight. The present invention provides a solution to this.

[0011] State of the art methods apply a treatment beam source whichgenerates a round intensity profile, this intensity profile is either ofa gaussian or near gaussian shape or of a so called top hat structurewhich is characterized by a very sharp edged rise and fall of theintensity at the edges and a near constant intensity in the middle. Inany case, the created variable spot size is of a round shape. Obviously,the shape of the treatment zone is not necessarily round. In the mostsimple case, it has an oval or a slit form, but typically the shape ofthe area needing treatment is of a more complicated structure. Since, instate of the art devices and methods to perform fundus treatments, thereis a very large error in treatment areas anyway, there has been no needfor generating a better overlap of the treatment zone and the treatmentbeam spot area. This is addressed in the present invention now that thetreatment beam is more accurately formed and projected onto thetreatment zone.

[0012] A general problem in laser based fundus treatment is the movementof the eyeball during the treatment. From clinical studies the optimalillumination times are known, but during treatment it must be assuredthat the treatment zone is illuminated for this period. State of the artsolutions operated with an real time viewing by the operator by means ofa fundus viewing ocular. The device further provides means for theoperator to switch the treatment beam source on an off and thus tocontrol the beam source such, that the illumination is only working, ifthe treatment zone is within a certain region. This method is apotential source of inaccuracy, because both, the beam and the treatmentzone are barely visible during the treatment. The present inventionprovides a solution to this and the several problems identified above.

OBJECTS AND SUMMARY OF THE INVENTION

[0013] It is an object of the invention to provide a method ofaccurately adjusting the laser beam spot size to the treatment area foreach specific eyeball.

[0014] It is another object of the invention to determine the exactlythe size of the treatment zone from a digital processing of angiographyand slit lamp image.

[0015] It is yet another object of the invention, to provide an deviceto achieve significantly better overlap of the treatment zone and thetreatment beam spot area.

[0016] It is further an object of the invention to provide an deviceallowing an accurate viewing and means for automatic switching of thebeam source depending on the eye movement as well as a device capable ofadjusting the spot area in real time according to the eye movement.

[0017] Briefly stated, the present invention provides a system andmethod to accurately treat sites on an eye's retina employing computerbased image generation, processing and central control means inconjunction with diode laser sources and optical fibers. The system andmethod accurately determine geometry of a treatment zone of a specificeye's fundus and adjust a treatment beam to irradiate the treatment zonewith minimal coverage of adjacent well tissue. The treatment zone orzone is accurately determined with digital processing of angiographicdata and slit lamp image data. This information is integrated withinformation on the treatment beam characteristics to better matchtreatment beam coverage with minimal overlap with healthy areas of thefundus. Additionally preferred embodiments also have the ability toautomatically track eye movement and switch the beam source depending oneye movement, adjusting the beam spot area in real time.

[0018] The above, and other objects, features and advantages of thepresent invention will become apparent from the following descriptionread in conjunction with the accompanying drawings, in which likereference numbers in different drawings denote like items.

BRIEF DESCRIPTION OF THE FIGURES

[0019]FIG. 1 illustrates the general setup of a device for treatment ofan eye's fundus.

[0020]FIG. 2 illustrates integration of digital image processing meansinto a device for fundus treatment.

[0021]FIG. 3 shows a variable aperture imaging method to obtain a sharpedged intensity profile of variable beam spot area on a retina.

[0022]FIG. 4 illustrates implementation of a scanner system withsuitable optical imaging means in order to obtain a sharp edgedintensity profile of arbitrary beam spot area on a retina.

[0023]FIG. 5 illustrates implementation of an optical system including atwo dimensional movable beam source in the device in order to obtain asharp edged intensity profile of arbitrary beam spot area on a retina.

[0024]FIG. 6 contains an alternative device for the displacement of thelaser beam to treat a two dimensional treatment area.

[0025]FIG. 7 illustrates the use of a telescope to vary beam spot sizeinto the device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0026] The accuracy of the treatment of the fundus of an eye can bedrastically enhanced by the combination of diagnostic means with atherapeutic setup. The therapeutic setup consists of a light source,preferably a fiber coupled diode laser and a suitable optical systemswhich allows one to vary the spot size generated on the retina. Thediagnostic device is preferably a slit lamp with an additional opticalsetup to allow direct fundus viewing through an eyepiece andsimultaneously the generation of a digital image of the fundus. Thedigital image of the fundus is grabbed by a computer based imageprocessor and an image generation device, preferably a CCD camera. Fromthis image the size of the treatment zone can be determined andelectronically processed. The treatment beam spot area is variable and adigital image of the fundus is generated with the a simulation of thetreatment beam at a fixed position of the treatment beam spot areavarying optical system. From these two images it is possible to adjustthe treatment beam spot area to the actual treatment zone size.

[0027] Further, if the treatment zone is not sufficiently clearlydefinable in the generated diagnostic image, it is a subject of theinvention to include a digital image generated by means of fluorescenceangiography, align this image which is characterized by an extremelyhigh quality to the image obtained by the diagnostic means in theclaimed treatment device and determine the necessary treatment beam spotsize from the treatment zone area that is visible in the image obtainedby fluorescence angiography.

[0028] All points mentioned can be either implemented in an automaticway or require manual settings by the operator, or be realized in acombination. Several methods to generate a variable beam spot area onthe retina are also subjects of the invention.

[0029]FIG. 1 illustrates the setup of the whole device with all elementsthat are necessary to perform treatments of age related maculadegeneration by optical means. For reasons of simplicity only the basicelements of the patients eye one are included in the figure, which areretina 2 and lens 3. On retina 2 an image is formed which is originatedby optical radiation entering the eye being imaged basically by lens 3.For successful laser treatment contact lens 4 is placed at the cornea ofthe patients eye which minimizes possible eye movements and enables thelaser radiation to enter the eye with out damaging the cornea and withenhanced imaging properties. Also for reasons of simplicity the complexoptical system present in contact lens 4 is not shown. In any casecontact lens 4 has a certain refractive power as is well known in stateof the art laser treatment of the retina. Several different kinds ofradiation are imaged on retina 2. One is treatment laser radiation 5.This radiation is originated by laser system 14, preferably a diodelaser and coupled into optical fiber 13 which has a well defined corediameter and numerical aperture. Optical fiber 13 is a preferredelement, because it simplifies the device and helps to shape treatmentradiation 5 to the desired “top-hat” form with very sharp rising andfalling intensity profiles at the edges and a plateau like near constantintensity elsewhere. Radiation 5 emitting from the fiber end iscollimated by an optical system and optionally imaged to obtain adesired beam profile. None of these optics is a necessity, in fact quitea number of possible systems with an arbitrary number of lenses or evenwithout any lenses can be used according to the targeted problem.

[0030] Beam source 14 uses another feature: it contains an opticalsystem which allows for coupling the radiation of a secondary lightsource into optical fiber 13. This secondary light source preferably hasa different wavelength and typically provides a much lower optical powerthan the treatment source. This additional light source bears theadvantage that the visibility and thus the viewing possibilities areenhanced drastically because, due to the retina's opticalcharacteristics, the treatment beam is sometimes hard to observe. Usingviewing sources at a different wavelength resolves this problem, becausethe wavelength can be chosen in order to obtain the maximum viewingquality. Optional viewing radiation 16 is preferably imaged via opticalsystem 10 as is treatment beam radiation 5 itself. For reasons of bettervisibility the secondary radiation is illustrated on a different opticalpath parallel to the primary radiation, though it can in general alsotake the same path depending on the optics.

[0031] Both types of radiation pass through beam adjustment device 12.The secondary radiation creates image 11 on the retina, which does notnecessarily coincide with image 15 created by the treatment radiationitself. Never the less, since the radiation properties are known, it ispossible to determine the treatment image from the secondary image.

[0032] The design of optical system 12 is a subject of the invention andis now described in detail. Common to all these embodiments is thatadjustments by optical system 12 are not static ones but are variable tocreate variable images on retina 2 that have varying beam spot areas. Itis common in laser based eye treatment methods to allow simultaneousviewing {inspection) of retina 2. Therefore, means of a slit-lamp areincluded in the device. In its simplest form, a slit lamp consists oflight source 8 with a collimating optical system generating illuminationradiation 7 with suitable optical characteristics. Mirror 9 is locatedat 45 degree with respect to the optical axis. The purpose of mirror 9is to image the illumination into the eye. The illuminated area can beviewed along mirror 9 with back propagating image radiation 17 passingthe slit of mirror 9 and entering optical system 18 fulfilling imagingpurposes. Radiation 7 is chosen such, that it can pass through dichroicmirror 6 which is chosen highly reflective for treatment radiation 5 andoptional secondary radiation 16, but not totally reflective, hence smallparts of both, the treatment radiation 5 and secondary radiation 16returning from retina 2 can pass through the mirror and contribute tothe viewing means. Additional filters 19 can be optionally included inthe path of viewing radiation 17 in order to enhance the quality orobserving selectively only the result of one kind of radiation. Beamsplitting means 20 is placed in the general optical system behindprimary optics 18. A part of the radiation is mirrored into firstsecondary optical system 23 which creates an image on the detector areaof digital image generation means 24, preferably a CCD camera. Anotherset of filters 19 can be applied in the path. The other part contributesvia secondary optics 21 to a direct viewing by the operator, preferablya physician, via ocular 22.

[0033] As described earlier, the state of the art suffers from severaldeficiencies which basically originate from the fact that the area ofthe treatment zone cannot be determined accurately and thus alltreatment beam spot size variation methods are rudimentary and producean error up to 600%.

[0034] One significant innovation being subject of the invention hasalready been mentioned above: beam area generation means 10 are of amore sophisticated nature than in the prior art. FIG. 2 shows moreelements that are part of the device to allow highly accurate treatmentof the fundus of an eye. A central processing unit, preferably a PC in adesktop or an embedded form is used to control the incoming data fromviewing devices 24 and to control the beam area generating variableoptical system 12 accordingly. One or more display units 27 areconnected to processing unit 25 to display the viewing data, externaldata and to perform operations in order to optimize the treatmentprocedure. To minimize the error in the treatment mentioned above, thedevice is such, that in several steps the treatment area is firstdetermined in a relative way concerning the optical system beingresponsible for imaging the treatment beam to the retina and then thebeam spot area is adjusted in the same relative way. This avoids a largesource of error in the prior art, because the operator takes thetreatment area from an image generated with fluorescence generated underdifferent conditions, than present in the laser treatment device and inparticular not very well known. To overcome this, a digital image usingslit-lamp device 9 and digital image generation means 24 is taken.Further, another digital image is taken with the retina irradiatedpreferably by secondary light 16 with the optical system beingresponsible for setting up the treatment beam area on the retina in apre-determined basic position. Alternatively, the treatment beam lightcan itself can be used, but at significantly lower radiation power.However, due to reasons of visibility explained above, the use of asecondary light source is preferred. From this image the spot size oftreatment beam 5 can be precisely calculated in relative coordinates tothe slit lamp generated image. Further, a digital image withouttreatment radiation 5 or secondary radiation is taken at near equaltime, meaning that the image is taken within a time interval shortenough to assure, that the eye did not move. Alternatively a true equaltime image can be taken using either digital image filtering means orusing real filters and more than one digital image recording device.From this image the treatment zone may be determined with sufficientaccuracy. If so, the operator marks the treatment zone with a simplesoftware tool and the computer calculates the accurate size andcoordinates. Applying a simple method, the operator can then use thisdata to manually adjust the beam area spot size with suitable opticalsystem 12, which may be guided by electronic aids such as acoustical oroptical signals. An even more accurate method is to have centralprocessing unit 25 control optical system 10. The treatment beamparameters are also provided by central processing unit 25. The operatorcan now use manual positioning means 28 to locate the beam spot areacenter to a predetermined position within the treatment zone, preferablythe center or one of the edges. As in the prior art, he can stop andstart the treatment beam with a second external control, preferably afoot-piece, and simultaneously inspect the fundus in order to decide, ifthe treatment area and the treatment beam are aligned or if thisalignment has been disturbed by eye-movement. A significant differenceand advantage over the state of the art is, that the viewing can also bedone via the digital image generated in real-time and illustrated ondisplay unit 27. Digital image processing can enhance the image quality,and electronic image detection means 24 is more specifically sensitiveto the applied wavelengths.

[0035] Another subject of the invention is to align the image generatedby the slit-lamp means to a diagnostic image generated by means offluorescence angiography. Slit lamp generated images are generally ofmedium quality and, depending on the status of the disease and thespecific eyeball, the treatment zone can hardly be seen or may not bedetermined with sufficiently high accuracy. Therefore a digitalangiography image is loaded onto central processing means 25 anddisplayed on display device 27. As before, simultaneously or quasisimultaneously a slit lamp image is taken with and without the treatmentbeam spot and also displayed for the operator. From a minimum of twocharacteristic points like blood vessel crossings which may be marked bythe operator himself, the central processing unit aligns the two images,since they are in general of different form, because the optics or theeye position may vary. The operator further marks the treatment zone inthe angiography image, which can be done with high accuracy. Thesecoordinates are then calculated back to coordinates of the slit lamppicture and the system is able to calculate how optical system 12responsible for the treatment beam spot generation must be adjusted inorder to achieve high overlap accuracy. As described above, theadjustment can be performed manually with possibly electronic aids orfully automatically. In a preferred embodiment the complete adjustment,including the positioning of the beam spot to the treatment area, thetreatment process and the treatment control is performed automaticallyby the central processing unit on the basis of a real-time viewing ofthe retina with the digital image processing means.

[0036]FIG. 3 illustrates a preferred embodiment for optical device 12which is responsible for the generation of the treatment beam area. Thetreatment beam is produced by primary beam source 14 and preferablycoupled into optical fiber or light guide 13 to be shaped to the desiredtop hat intensity profile and to be transported with simple means fromprimary beam source 14 to the treatment device allowing the beam sourceto be spatially separated, which is of particular importance for lasersources due to safety requirements. From there primary radiation 5illuminates aperture 31. The radiation can illuminate aperture 31 eitherin a direct way or be imaged via suitable optical elements, preferablyforming a telescope, to produce a fixed spot on aperture 31. Inparticular, radiation 5 can be collimated optimally in order to minimizethe divergence angle. Aperture 31 cuts a defined section from said beam.This cut has, apart from diffraction limits, a sharp intensity edges,what is of great advantage to the treatment process, because it assuresthat all parts of the treatment zone are irradiated with the sameenergy. Aperture 31 is adjustable whether via mechanical means likemicrometer screws to be moved via the operator directly or viaelectromechanical means 34 like step motors or piezo actuators. Means 34can be controlled via the operator directly with suitable controldevices or via central processing unit 25 they are connected with viainterface lines 35. More than one aperture may be included within thesetup, one of which 32 is illustrated in FIG. 3. This apertures can becontrolled in the same manner as the primary aperture and serve forvarious purposes. One is the generation of a two dimensional irradiationsurface on the retina which is of higher complexity than the simplecircle, that would be the best choice for single aperture 31. Forexample the combination of a circular aperture with a slit apertureallows near-oval irradiation spots or two slit apertures allowrectangular forms. In a preferred embodiment the whole aperture unit isexchangeable, hence the operator can choose a certain combination inorder to adjust the image to the treatment beam area which is visiblefrom the diagnostic fluorescence angiography. Common to the opticalsystem is as already mentioned the basic position. For the case of theaperture based solution to the adjustment of beam spot size to treatmentzone size basic position of electromechanical dislocation means 34 isdirectly related to a certain basic aperture size of apertures 31 and 32or eventually more. This size is first illuminated with secondary beam16 and the radiation passing the aperture propagates to the eyepiecefor, or is optionally imaged via optical system 33. The image of theaperture on the retina is then recorded and digitized. This digitalimage is one of the basic images mentioned above to perform thecalibration. Therefore, secondary beam 16 must be coupled into thepropagation path of primary radiation 5. This is done in a unique andwell known way in order to have a well defined system of coordinates tocompute from secondary beam retina image 11 to primary beam shape 15 andits spot size, in a preferred embodiment secondary beam 16 is alreadycoupled to optical fiber 13 together with the treatment beam. Theoperator can then use primary beam 5 to chose the exact position of thetreatment zone and start the process. This is performed as describedabove utilizing the means illustrated in FIG. 2.

[0037]FIG. 4 illustrates a more advanced system for the generation ofthe treatment beam area on the retina. State of the art methods sufferfrom the deficiency that they produce round spots since optical fibers,laser profiles or lamp emitted radiation generally produce round spots.These spots are then shaped and imaged to the retina. The new methodillustrated in FIG. 3 and described above already is a significantinnovation over the state of the art, since it allows other than roundprofiles. Additionally, the treatment beam is kept at small sizes andthus there is no longer a requirement for a rectangular top hatintensity profile. However, the treatment zone usually has a much morecomplicated form. In the prior art, the treatment zone could not bedetermined with sufficient accuracy, hence there was no need for thegeneration of an accurate treatment beam area. By the methods of thisinvention the treatment zone becomes well known, hence the mechanisms toilluminate said treatment zone can be enhanced in the same degree. FIG.4 basically consists of the components described above, but adjustingoptical system 12 is embodied as a scanning device. In its most basicform a scanner contains two movable mirrors 36 and 37 positioned in anorthogonal way. The angle relative to the optical axis of each mirror isadjustable in one dimension, hence according to their orthogonalposition by independent angle variation the beam can be positioned to anarbitrary position on a two dimensional surface. This surface canfurther be imaged and such an imaging is performed via contact lens 4and the eyelens onto the retina. Source 14 can be collimated, optionallybe expanded to the desired diameter with suitable optical system 10 andthen be directly imaged by the scanning means.

[0038] The eye lens and the original beam diameter hitting the eye lensare responsible for the size of the beam spot on the retina, on whichthe beam delivered by the treatment beam spot is dependent on the beamdiameter and divergence angle when it hits the contact lens and on thecontact lens itself. By varying the contact lens and the beam propertiesby means of adjustable optical system 10 the beam spot on the retina canbe varied accordingly. For use with a scanner the beam is of relativelylow power and small size. If the scan velocity is chosen sufficientlylarge, each spot on the treatment zone is impinged by a sufficientlylarge number of photons for an optimal treatment process.

[0039] To generate a true image of the treatment zone determined by useof the methods described above, two ways can be followed. The firstconsists in the generation of a rectangular image and switching theprimary beam source on and off sufficiently fast, hence simply nointensity is emitted if the scanner positions a point out of thetreatment zone and the laser is on if the scanner positions a point onthe treatment zone. Hence even non connected treatment zones can bemapped accurately.

[0040] The second method is to operate the scanner in an asynchronousmode with interruption. Mirrors 36 and 37 do not just map a rectangle,they rather map the concrete form of the treatment zone. This enhancesthe scanning efficiency and lowers the requirements to the switchingvelocity of primary beam source 14. However, the requirements to thescanner deflection properties rise.

[0041] Scanner deflection can be implemented by various methods, twocommons are to include galvanometric driven mirrors and piezo actuatordriven mirrors.

[0042] Principally, instead of two orthogonal one dimensional deflectingmirrors a single two dimensional deflecting mirror can be used. Ascanner system can be even of higher complexity. Today, micro-mirrordevices are commercially available, for example by Texas Instruments,Inc. of Houston, Tex. which consist of a two dimensional array of micromirrors. These devices are able to produce pixel based 2-dimensionalimage structure which can be used for display technologies, in micromachining and for applications in medicine. A device of this type isincluded as the basic element of adjusting optical system 12, optionallycombined with suitable optical elements to create optical images whichfulfill all the requirements given by the micro-mirror device and thetreatment zone. The micro-mirror device is directly controlled bycentral processing unit 25. The image created directly propagates viathe optics and contact lens 4 to the retina.

[0043] An equivalent effect to the micro mirror method can be achievedusing liquid crystal devices and polarizers, similar to the use ofliquid crystal devices in printing, display and lithographyapplications. Adjusting optical system 12 then contains an optical setupwhich is a liquid crystal modulation device which allows to generate animage formed by a sufficiently large number pixels of that matches thetreatment zone. It is obvious, that any image generation means can beincluded in a treatment setup to generate the treatment zoneillumination beam area.

[0044] The optics further can be positioned externally by the operatorfor example using positioning means 28. In particular, said positioningto treatment zone is enhanced by using the secondary beam source asaiming beam and using the digital image recording and processing meansdescribed above. The switching the laser on and off is performed in anThe use of a scanner system as described only makes sense if it isoperated with a sufficiently fast driving electronics and controlled bya computer based system. The inclusion of a system of this type and theconnection of all variable elements to the central processing unit isalso a subject of the invention.

[0045]FIG. 4 shows another innovative method for the generation ofvariable image on the retina. From the point of the operator and thepatient, this method provides an equivalent interface for the treatmentitself and the result will also be comparable to the results obtained byusing scanner methods. In fact the scanning facility is maintained, butin this case secondary light source 16 itself, if directly included inthe treatment setup, or the emitting end of fiber 13 if the beam sourceis external and it's produced radiation is transported to the treatmentdevice by fiber 13, is moved along a special path. This movement can, aswith the scanning method before, follow a complicated path directly orfollow a rasterized rectangle. Primary light source 14 is switchedaccording to the treatment size image requirements. To generate themovement of, for example, the fiber end, a two dimensional scanning unitcan be constructed either mechanically, electro-mechanically by theapplication of piezo actuators or by a combination of these. In FIG. 5,fiber 13 is connected to mount 36. Mount 36 is fixed on two dimensionaldisplacement unit 40. Actuators 41, preferably piezo actuators, causethe appropriate movements and are connected with central processing unit25 by connection lines 35. Since aiming beam 16 produced by the fiber ispreferably transported by said fiber it follows the same contour astreatment beam 5 and can thus be still used for all purposes mentionedabove. The optical system images the plane, in which the fiber end movesto the retina. Optionally, the optical system can be variedautomatically by central control unit 25 or be exchangeable in order toachieve different imaging relations.

[0046]FIG. 6 illustrates another element which can be implemented in theoptical path to achieve the desired beam displacement. Incomingtreatment beam 5 passes parallel plate 42 optionally coateddielectrically in order to minimize losses. This plate is mountedmovably with one reference point on cylinder 47. Relative to thisreference point the plate can now be rotated for a certain angle byactuator 49, which can be a simple stepper or, preferably, a piezoactuator, which is in suitable contact with parallel plate 42. Inparticular it must allow a certain linear movement of the actuatingpoint. Because of this angle, incoming beam 5 is displaced by a certaindistance hence outgoing beams 45 and 46 are parallel the incoming beam,but displaced by different distances according to the angle at which theplate is positioned within the beam. If the plate is in the positionmarked by feature 43 it creates a smaller displacement in particularbeam 45, than if it is in the position marked by feature 44, wheredisplaced beam 46 is uniquely given by a mathematical relation betweenthe displacement and the angle and can hence be controlled accurately.The two dimensional displacement can be obtained either by the use oftwo orthogonal devices each producing a displacement in one direction ora single plate, which has one fixed reference point and two orthogonalvariable points. For this displacement unit all optical and electronicfeatures described above can be used.

[0047]FIG. 7 illustrates another embodiment of treatment optics. Primarylight source 14 creates treatment radiation 5, which is preferablycoupled into optical fiber 13 and transported to the treatment device,together with secondary radiation 17 which serves as aiming beam andpreferably has a different wavelength. The output 5 and 16 from fiber 13is preferably collimated by optical system 10 and then coupled intooptical system 52, which plays the role of adjusting optical system 12in prior embodiments. System 52 consists of the optical module of acommercial video camcorder, which is available as a component, as forexample the Sony ELI Series. In their original application these modulesare intended to generate images on a camera chip for different objectdistances, which is basically equivalent to the purpose required for thetreatment of the fundus of an eye. The optical states of module 52 canbe varied electronically through interface 35 and central processingunit (not shown), which is preferably a PC. The reference image used forthe calibration of the angiography to the native fundus image isrecorded at a fixed position of the video module and with the dataobtained from the image calibration. The correct state is chosen inorder to generate a well defined treatment spot on the treatment zone.The principal treatment features are equivalent to the other embodimentsdescribed above. This method can in particular be combined with theaperture method which enhances the performance because it allows otherthan round profiles, the aperture creates top hat intensity structuresif desired and operated far from the diffraction limit and the processcan be implemented electronically and thus be controlled completely by acentral processing means simply.

[0048] Having described preferred embodiments of the invention withreference to accompanying drawings it is to be understood that theinvention is not limited to those precise embodiments, and that variouschanges and modifications may be effected therein by one skilled in theart without departing from the scope or the spirit of the invention asdefined in the appended claims.

1. An improved, accurate method of treatment of an eye's fundus, using atreatment optical system, preferably with a slit lamp assembly,comprising the steps of: generating a treatment beam from a primarylight source; generating a digital reference image, using a secondarylight source, on an eye's retina at a predetermined position of saidtreatment beam's imaging optical system; wherein said secondary lightsource preferably operates at a different wavelength from said primarylight source; controlling and processing said digital image by at leastone computer to accurately determine a treatment zone; wherein a nativedigital image of said fundus is simultaneously generated, and whereinsaid treatment zone is generated preferably by means of fluorescenceangiography; marking uniquely said treatment zone onto a correspondingregion of said native digital fundus image; adjusting said treatmentbeam and said treatment optical system to have said treatment beam coversaid treatment zone and optimally irradiate said treatment zone.
 2. Amethod of treatment of an eye's fundus according to claim 1, whereinsaid adjusting is accomplished by one of the following group of methods:manually completing by an operator, assisting with electronic means,preferably with optical or acoustical signals, and completing fullyautomatically.
 3. A method of treatment of an eye's fundus according toclaim 1, further comprising the steps of: aligning said native digitalfundus image with said image of said treatment zone by applying suitablemathematical algorithms to transform between coordinate systems forthese two images; wherein said aligning is accomplished by one of thefollowing methods: an automatically operating pattern recognitionscheme, and manually marking at least two reference points in eachimage; illuminating and imaging at least one variable aperture with anoptical system onto said treatment zone on said retina; and imaging saidtreatment beam onto said variable aperture and onto said retina tocreate various polygonal shapes.
 4. A method of treatment of an eye'sfundus according to claim 3, further comprising the step of:sequentially applying at least two apertures having different shapes togenerate said image on said retina in more complicated geometricalshapes than polygonal shapes.
 5. A method of treatment of an eye'sfundus according to claim 4, wherein said apertures are variedindependently of each other and can be adjusted manually,semi-automatically or automatically to a desired size.
 6. A method oftreatment of an eye's fundus according to claim 3, further comprisingthe step of: further adjusting of said optical system imaging saidtreatment beam by scanning with at least two variable, linear,orthogonal-arranged devices and using an automatic primary beam powerswitch to create an arbitrary-shaped two dimensional regionsubstantially equivalent to said treatment zone.
 7. A method oftreatment of an eye's fundus according to claim 4, wherein said scanningof said treatment beam over said treatment zone irradiates each point inthe treatment zone for a predetermined period of time.
 8. A method oftreatment of an eye's fundus according to claim 6, wherein said furtheradjusting is accomplished by one of the following group of methods:manually completing by an operator, assisting with electronic means,preferably with optical or acoustical signals, and completing fullyautomatically.
 9. A method of treatment of an eye's fundus according toclaim 1, wherein said secondary light source operates preferably at agreen wavelength; and wherein said secondary light source produces ageometrical image other than a spot and preferably said geometricalimage contains at least one of the following group of shapes: a ringshape, and a cruciform shape.
 10. A method of treatment of an eye'sfundus according to claim 3, wherein said imaging of said treatment beamis positioned manually on said retina, preferably being positioned thereby at least one secondary target spot and wherein said native digitalimage of the fundus is generated in real time, and said position of saidtreatment spot area is determined electronically and transformed intosaid coordinate system of said diagnostic fluorescence angiography anddisplayed thereon.
 11. A method of treatment of an eye's fundusaccording to claim 10, wherein in real time said position of saidtreatment zone is determined and said treatment light source isappropriately switched on and off, wherein said native image of saidfundus containing said spot of said treatment beam and said imagegenerated diagnostically by fluorescence angiography means are digitallyprocessed, superimposed and presented on a display device, and whereinin real time said position of said treatment zone is determined and saidtreatment beam spot is positioned in real time according to saidtreatment beam spot position.
 12. A method of treatment of an eye'sfundus according to claim 11, wherein in real time a position of a pointon said retina or said cornea, rather than on said treatment zone, isdetermined and said position of aid treatment zone is calculatedtherefrom.
 13. A method of treatment of an eye's fundus according toclaim 1, further comprising the step of: varying power of said treatmentbeam generated by said primary light source to allow for optical lossesoccurring along said optical path in order to keep constant power onsaid retina.